1. Field of the Invention
The present invention relates to an aircraft probe for measuring aerodynamic parameters of the ambient flow of the aircraft, comprising a wind vane mounted for rotation on the aircraft which is adapted to align itself in the direction of the flow and is provided with means for detection of differential pressure representative of the aerodynamic incidence of the wind vane, and means for determining the direction of the wind vane with respect to the aircraft.
2. Description of Related Art
The piloting of any aircraft involves knowing its relative speed with respect to the air, that is to say to the relative wind. This speed is determined by means of detectors of the static pressure po, of the total pressure pt, of the angle of incidence .alpha. and of the angle of sideslip .beta.. .alpha. and .beta. supply the direction of the velocity vector in a reference or referential system related to the aircraft and pt - po supplies the module of this speed vector. The four aerodynamic parameters, therefore, make it possible to determine the velocity vector of an airplane and, subsidiarily, of an aircraft with convertible rotor.
A probe of the above-mentioned type is already known from EP-A-O 176 405. It has the advantage of assuring several functions and of thus avoiding an excessive multiplicity of detectors which would be fragile, the maintenance of which would have to be assured and which would consume de-icing energy. It also has the advantage over static multi-functional probes with fixed antenna, for instance of the type described in U.S. Pat. No. 4,096,744, of offering relatively good precision, particularly at large angles of incidence.
In fact, the wind vane of the prior-art probe is subjected not only to the aerodynamic torque produced by the relative wind, but also to a frictional torque acting on its shaft, so that it does not orient itself precisely in the direction of the flow. In other words, the aerodynamic angle of incidence of the wind vane, that is to say the angle formed between the direction of flow and the plane of the wind vane, is not zero.
EP-A-0 176 405 teaches determining the angle of incidence of the wind vane by the differential pressure measurement and calculating the sum of this angle of incidence and the relative orientation of the wind vane with respect to the aircraft in order to obtain the true angle of incidence of the aircraft.
As a result, the operation of the probe of said publication, which, therefore, employs calculating means, is not the simplest and is rather expensive. This is a drawback for subsonic civilian planes.